37 research outputs found
PynPoint: a modular pipeline architecture for processing and analysis of high-contrast imaging data
The direct detection and characterization of planetary and substellar
companions at small angular separations is a rapidly advancing field. Dedicated
high-contrast imaging instruments deliver unprecedented sensitivity, enabling
detailed insights into the atmospheres of young low-mass companions. In
addition, improvements in data reduction and PSF subtraction algorithms are
equally relevant for maximizing the scientific yield, both from new and
archival data sets. We aim at developing a generic and modular data reduction
pipeline for processing and analysis of high-contrast imaging data obtained
with pupil-stabilized observations. The package should be scalable and robust
for future implementations and in particular well suitable for the 3-5 micron
wavelength range where typically (ten) thousands of frames have to be processed
and an accurate subtraction of the thermal background emission is critical.
PynPoint is written in Python 2.7 and applies various image processing
techniques, as well as statistical tools for analyzing the data, building on
open-source Python packages. The current version of PynPoint has evolved from
an earlier version that was developed as a PSF subtraction tool based on PCA.
The architecture of PynPoint has been redesigned with the core functionalities
decoupled from the pipeline modules. Modules have been implemented for
dedicated processing and analysis steps, including background subtraction,
frame registration, PSF subtraction, photometric and astrometric measurements,
and estimation of detection limits. The pipeline package enables end-to-end
data reduction of pupil-stabilized data and supports classical dithering and
coronagraphic data sets. As an example, we processed archival VLT/NACO L' and
M' data of beta Pic b and reassessed the planet's brightness and position with
an MCMC analysis, and we provide a derivation of the photometric error budget.Comment: 16 pages, 9 figures, accepted for publication in A&A, PynPoint is
available at https://github.com/PynPoint/PynPoin
MIRACLES: atmospheric characterization of directly imaged planets and substellar companions at 4-5 m. II. Constraints on the mass and radius of the enshrouded planet PDS 70 b
The circumstellar disk of PDS 70 hosts two forming planets, which are
actively accreting gas from their environment. In this work, we report the
first detection of PDS 70 b in the Br and filters with VLT/NACO, a
tentative detection of PDS 70 c in Br, and a reanalysis of archival
NACO and SPHERE and imaging data. The near side of the disk is
also resolved with the Br and filters, indicating that scattered
light is non-negligible at these wavelengths. The spectral energy distribution
of PDS 70 b is well described by blackbody emission, for which we constrain the
photospheric temperature and photospheric radius to K and . The relatively low bolometric
luminosity, , in combination with the large
radius, is not compatible with standard structure models of fully convective
objects. With predictions from such models, and adopting a recent estimate of
the accretion rate, we derive a planetary mass and radius in the range of
and
, independently of the age and post-formation entropy of the
planet. The blackbody emission, large photospheric radius, and the discrepancy
between the photospheric and planetary radius suggests that infrared
observations probe an extended, dusty environment around the planet, which
obscures the view on its molecular composition. Finally, we derive a rough
upper limit on the temperature and radius of potential excess emission from a
circumplanetary disk, K and
, but we do find weak evidence that the current data favors a
model with a single blackbody component.Comment: 19 pages, 7 figures, accepted for publication in A&
Comparing Apples with Apples: Robust Detection Limits for Exoplanet High-Contrast Imaging in the Presence of non-Gaussian Noise
Over the past decade, hundreds of nights have been spent on the worlds
largest telescopes to search for and directly detect new exoplanets using
high-contrast imaging (HCI). Thereby, two scientific goals are of central
interest: First, to study the characteristics of the underlying planet
population and distinguish between different planet formation and evolution
theories. Second, to find and characterize planets in our immediate Solar
neighborhood. Both goals heavily rely on the metric used to quantify planet
detections and non-detections.
Current standards often rely on several explicit or implicit assumptions
about the noise. For example, it is often assumed that the residual noise after
data post-processing is Gaussian. While being an inseparable part of the
metric, these assumptions are rarely verified. This is problematic as any
violation of these assumptions can lead to systematic biases. This makes it
hard, if not impossible, to compare results across datasets or instruments with
different noise characteristics.
We revisit the fundamental question of how to quantify detection limits in
HCI. We focus our analysis on the error budget resulting from violated
assumptions. To this end, we propose a new metric based on bootstrapping that
generalizes current standards to non-Gaussian noise. We apply our method to
archival HCI data from the NACO-VLT instrument and derive detection limits for
different types of noise. Our analysis shows that current standards tend to
give detection limit that are about one magnitude too optimistic in the
speckle-dominated regime. That is, HCI surveys may have excluded planets that
can still exist.Comment: After first iteration with the referee, resubmitted to AJ. Comments
welcome
CROCODILE \\ Incorporating medium-resolution spectroscopy of close-in directly imaged exoplanets into atmospheric retrievals via cross-correlation
The investigation of the atmospheres of closely separated, directly imaged
gas giant exoplanets is challenging due to the presence of stellar speckles
that pollute their spectrum. To remedy this, the analysis of medium- to
high-resolution spectroscopic data via cross-correlation with spectral
templates (cross-correlation spectroscopy) is emerging as a leading technique.
We aim to define a robust Bayesian framework combining, for the first time,
three widespread direct-imaging techniques, namely photometry, low-resolution
spectroscopy, and medium-resolution cross-correlation spectroscopy in order to
derive the atmospheric properties of close-in directly imaged exoplanets. Our
framework CROCODILE (cross-correlation retrievals of directly imaged
self-luminous exoplanets) naturally combines the three techniques by adopting
adequate likelihood functions. To validate our routine, we simulated
observations of gas giants similar to the well-studied ~Pictoris~b
planet and we explored the parameter space of their atmospheres to search for
potential biases. We obtain more accurate measurements of atmospheric
properties when combining photometry, low- and medium-resolution spectroscopy
into atmospheric retrievals than when using the techniques separately as is
usually done in the literature. We find that medium-resolution () K-band cross-correlation spectroscopy alone is not suitable to constrain
the atmospheric properties of our synthetic datasets; however, this problem
disappears when simultaneously fitting photometry and low-resolution () spectroscopy between the Y and M bands. Our framework allows the
atmospheric characterisation of directly imaged exoplanets using the
high-quality spectral data that will be provided by the new generation of
instruments such as VLT/ERIS, JWST/MIRI, and ELT/METIS
ISPY-NACO Imaging Survey for Planets around Young stars. The demographics of forming planets embedded in protoplanetary disks
We present the statistical analysis of a subsample of 45 young stars
surrounded by protoplanetary disks (PPDs). This is the largest imaging survey
uniquely focused on PPDs to date. Our goal is to search for young forming
companions embedded in the disk material and to constrain their occurrence rate
in relation to the formation mechanism. We used principal component analysis
based point spread function subtraction techniques to reveal young companions
forming in the disks. We calculated detection limits for our datasets and
adopted a black-body model to derive temperature upper limits of potential
forming planets. We then used Monte Carlo simulations to constrain the
population of forming gas giant companions and compare our results to different
types of formation scenarios. Our data revealed a new binary system (HD38120)
and a recently identified triple system with a brown dwarf companion orbiting a
binary system (HD101412), in addition to 12 known companions. Furthermore, we
detected signals from 17 disks, two of which (HD72106 and TCrA) were imaged for
the first time. We reached median detection limits of L =15.4 mag at 2.0
arcsec, which were used to investigate the temperature of potentially embedded
forming companions. We can constrain the occurrence of forming planets with
semi-major axis a in [20 - 500] au and Teff in [600 - 3000] K, in line with the
statistical results obtained for more evolved systems from other direct imaging
surveys. The NaCo-ISPY data confirm that massive bright planets accreting at
high rates are rare. More powerful instruments with better sensitivity in the
near- to mid-infrared are likely required to unveil the wealth of forming
planets sculpting the observed disk substructures.Comment: 25 pages, 16 figures, 3 tables, accepted for publication in A&
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b
We present the highest fidelity spectrum to date of a planetary-mass object.
VHS 1256 b is a 20 M widely separated (8\arcsec, a =
150 au), young, planetary-mass companion that shares photometric colors and
spectroscopic features with the directly imaged exoplanets HR 8799 c, d, and e.
As an L-to-T transition object, VHS 1256 b exists along the region of the
color-magnitude diagram where substellar atmospheres transition from cloudy to
clear. We observed VHS 1256~b with \textit{JWST}'s NIRSpec IFU and MIRI MRS
modes for coverage from 1 m to 20 m at resolutions of 1,000 -
3,700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium
are observed in several portions of the \textit{JWST} spectrum based on
comparisons from template brown dwarf spectra, molecular opacities, and
atmospheric models. The spectral shape of VHS 1256 b is influenced by
disequilibrium chemistry and clouds. We directly detect silicate clouds, the
first such detection reported for a planetary-mass companion.Comment: Accepted ApJL Iterations of spectra reduced by the ERS team are
hosted at this link:
https://github.com/bemiles/JWST_VHS1256b_Reduction/tree/main/reduced_spectr
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems IV: NIRISS Aperture Masking Interferometry Performance and Lessons Learned
We present a performance analysis for the aperture masking interferometry
(AMI) mode on board the James Webb Space Telescope Near Infrared Imager and
Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables,
AMI accesses inner working angles down to and even within the classical
diffraction limit. The scientific potential of this mode has recently been
demonstrated by the Early Release Science (ERS) 1386 program with a deep search
for close-in companions in the HIP 65426 exoplanetary system. As part of ERS
1386, we use the same dataset to explore the random, static, and calibration
errors of NIRISS AMI observables. We compare the observed noise properties and
achievable contrast to theoretical predictions. We explore possible sources of
calibration errors, and show that differences in charge migration between the
observations of HIP 65426 and point-spread function calibration stars can
account for the achieved contrast curves. Lastly, we use self-calibration tests
to demonstrate that with adequate calibration, NIRISS AMI can reach contrast
levels of mag. These tests lead us to observation planning
recommendations and strongly motivate future studies aimed at producing
sophisticated calibration strategies taking these systematic effects into
account. This will unlock the unprecedented capabilities of JWST/NIRISS AMI,
with sensitivity to significantly colder, lower mass exoplanets than
ground-based setups at orbital separations inaccessible to JWST coronagraphy.Comment: 20 pages, 12 figures, submitted to AAS Journal
The \textit{JWST} Early Release Science Program for Direct Observations of Exoplanetary Systems III: Aperture Masking Interferometric Observations of the star HIP\,65426 at
We present aperture masking interferometry (AMI) observations of the star HIP
65426 at as a part of the \textit{JWST} Direct Imaging Early
Release Science (ERS) program obtained using the Near Infrared Imager and
Slitless Spectrograph (NIRISS) instrument. This mode provides access to very
small inner working angles (even separations slightly below the Michelson limit
of for an interferometer), which are inaccessible with the
classical inner working angles of the \textit{JWST} coronagraphs. When combined
with \textit{JWST}'s unprecedented infrared sensitivity, this mode has the
potential to probe a new portion of parameter space across a wide array of
astronomical observations. Using this mode, we are able to achieve a contrast
of \,mag relative to the host star at a separation
of {\sim}0.07\arcsec but detect no additional companions interior to the
known companion HIP\,65426\,b. Our observations thus rule out companions more
massive than 10{-}12\,\rm{M\textsubscript{Jup}} at separations
from HIP\,65426, a region out of reach of ground or
space-based coronagraphic imaging. These observations confirm that the AMI mode
on \textit{JWST} is sensitive to planetary mass companions orbiting at the
water frost line, even for more distant stars at 100\,pc. This result
will allow the planning and successful execution of future observations to
probe the inner regions of nearby stellar systems, opening essentially
unexplored parameter space.Comment: 15 pages, 9 figures, submitted to ApJ Letter
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The JWST Early-release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 μ m Spectrum of the Planetary-mass Companion VHS 1256–1257 b
We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a MJup widely separated (∼8″, a = 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color–magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256 b with JWST's NIRSpec IFU and MIRI MRS modes for coverage from 1 to 20 μm at resolutions of ∼1000–3700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the JWST spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. IV. NIRISS Aperture Masking Interferometry Performance and Lessons Learned
We present a performance analysis for the aperture masking interferometry (AMI) mode on board the James Webb Space Telescope Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables, AMI accesses inner working angles down to and even within the classical diffraction limit. The scientific potential of this mode has recently been demonstrated by the Early Release Science (ERS) 1386 program with a deep search for close-in companions in the HIP 65426 exoplanetary system. As part of ERS 1386, we use the same data set to explore the random, static, and calibration errors of NIRISS AMI observables. We compare the observed noise properties and achievable contrast to theoretical predictions. We explore possible sources of calibration errors and show that differences in charge migration between the observations of HIP 65426 and point-spread function calibration stars can account for the achieved contrast curves. Lastly, we use self-calibration tests to demonstrate that with adequate calibration NIRISS F380M AMI can reach contrast levels of ∼9–10 mag at ≳λ/D. These tests lead us to observation planning recommendations and strongly motivate future studies aimed at producing sophisticated calibration strategies taking these systematic effects into account. This will unlock the unprecedented capabilities of JWST/NIRISS AMI, with sensitivity to significantly colder, lower-mass exoplanets than lower-contrast ground-based AMI setups, at orbital separations inaccessible to JWST coronagraphy